And I'm Robert Siegel. At congressional hearings this week, three witnesses introduced as State Department whistleblowers criticized the administration's handling of last September's assault on the U.S. mission in Benghazi, Libya. That attack claimed the life of United States Ambassador Chris Stevens and three other Americans.

The witnesses also criticized the investigation that the State Department conducted into those events. An Accountability Review Board was impaneled, chaired by a very senior retired diplomat, Thomas Pickering, and co-chaired by retired Chairman of the Joint Chiefs Admiral Mike Mullen.

Well, Thomas Pickering joins us now. Welcome to the program.

THOMAS PICKERING: Thank you, Robert.

SIEGEL: I should have said first that the Accountability Review Board that you chaired found, and I'm quoting her, systemic failures and leadership and management deficiencies at senior levels within two bureaus of the State Department that resulted in a security posture inadequate for Benghazi. Did you hear anything in Congress this week that added to or in any way changed what you learned in your investigation?

PICKERING: No, I did not.

SIEGEL: One complaint was that the investigation didn't go high enough. I want to play you - this is Congressman John Duncan of Tennessee questioning first Mark Thompson, who was the former deputy coordinator for State Department counterterrorism operations and also the deputy chief of mission in Tripoli, Gregory Hicks. First point, Mr. Thompson says he was never interviewed by you guys.

(SOUNDBITE OF HEARING)

REPRESENTATIVE JOHN DUNCAN: Mr. Thompson, what were you told was the reason you were not interviewed?

MARK THOMPSON: I was not given a reason, sir.

DUNCAN: You were not given a reason? Mr. Hicks, do you feel that the report lets any individual or bureaucracy off the hook?

GREGORY HICKS: Yes, sir, I think that in our system of government, the decision-making authority is at the level of presidentially appointed, Senate-confirmed individuals. That's at the level of assistant secretary or higher.

SIEGEL: That was Gregory Hicks, who was the D.C. - the deputy chief of mission in Libya. First point, was Thompson given a reason, as you describe it, or never given a reason for why he wasn't interviewed?

PICKERING: Yes, Mr. Thompson, like every other person in the State Department, received a notice from the secretary asking any with information to contribute to step forward and provide their willingness to be part of the activity of the investigation. He did not follow up, and as a result, he was not interviewed.

SIEGEL: What about this question that your review didn't look at people at the political level or the assistant secretary level of State?

PICKERING: We did, and of course, one of the individuals we had found who had failed in the performance of his duties was an assistant secretary. And our recommendation was that that person, as well as another person who made decisions of importance in this case, no longer continue in their jobs, and that apparently has happened.

SIEGEL: Gregory Hicks, the number two man at the embassy in Tripoli, also he related calling for military support to be dispatched to Benghazi, specifically air support.

(SOUNDBITE OF HEARING)

HICKS: We determined that we needed to send a second team from Tripoli to secure the airport for the withdrawal of our personnel from Benghazi after the mortar attack.

UNIDENTIFIED MAN: But were any of these U.S. military personnel not permitted to travel on a rescue mission or relief mission to Benghazi?

HICKS: They were not authorized to travel.

SIEGEL: Does that square with what your investigation found?

PICKERING: It squares with what we heard. By the time that relief plane arrived, it was the second aircraft, not the first, the wounded had all been moved and were either en route to Tripoli or nearly at Tripoli and where they needed the medical help.

The second question is were they needed in Tripoli, and of course, Mr. Hicks is the best judge of that. On the other hand, it was very clear that Tripoli itself had reduced security presence because a number of people accompanied the first plane to Benghazi, and overall there was continued and serious concern, as well, about the security at Tripoli.

SIEGEL: You're saying, Ambassador Pickering, that to have dispatched that second group to Benghazi would have made our staff at the embassy in Tripoli potentially that much more vulnerable?

PICKERING: It was, and that was on the basis of testimony we heard from people who were at Tripoli at the time.

SIEGEL: We should say here you were a career diplomat for many, many years and an ambassador in many hot spots. Do you regard this wave of hearings as a genuine effort to get at what might have been a scandalous misrepresentation of what happened in Benghazi, or as a political sideshow?

PICKERING: I believe, from my own personal experience, the latter is much more preeminent at this stage than the former, particularly as I listen to the hearings and found indeed very little that I thought added to certainly the issues we were concerned with.

SIEGEL: Should someone higher up have fallen on his or her sword and taken responsibility for the shortcomings that you and Admiral Mullen and your colleagues documented here?

PICKERING: The secretary did that on numerous occasions.

SIEGEL: Secretary of State Clinton, you're saying, has to your satisfaction taken responsibility for what happened?

PICKERING: Yes. She made it very clear in her public statements that she felt that she should take responsibility.

SIEGEL: Well, Ambassador Pickering, thank you very much for talking with us.

PICKERING: Thank you very much, Robert, it's good to talk to you, and I'm delighted that we've had this chance. I would like to mention one other thing, it has to do with the hearing and it has to do with the Accountability Review Board. It was mentioned, and it's frequently repeated, that I refused to testify to the hearing. That is not true.

Certainly I made every effort the day before the hearing, including through the White House and their legislative people, to seek an opportunity to join the team testifying before the committee. I was told through the White House that that had been rejected. I was offered a kind of consolation prize of some other time.

SIEGEL: You're saying that had been rejected, the White House told you that had been rejected...

PICKERING: Been rejected by the majority on the committee.

SIEGEL: On the Issa committee, yes.

PICKERING: The majority of the committee still continues to insist that I rejected them, which is not the case.

SIEGEL: If you were invited back to another hearing next week, the week after...

PICKERING: I would certainly go.

SIEGEL: You would appear. Well, Ambassador Pickering, thanks a lot for talking with us.

PICKERING: Thank you, Robert.

SIEGEL: That's retired Ambassador Thomas Pickering, who chaired the State Department's Accountability Review Board on Benghazi. He is a trustee and expert with the National Committee on American Foreign Policy. Transcript provided by NPR, Copyright NPR.